The present invention relates to a new and improved method for forming a snarl-free thread reserve as well as to an improved winding machine or winder for winding-up one or a number of threads or the like.
In winding machines, twisting machines and doubling machines or frames the threads are withdrawn so-to-speak overhead from an unwinding or delivery bobbin or spool. The threads are guided by a guide eye or eyelet which is arranged above the unwinding or delivery bobbin. Due to the centrifugal forces acting upon the thread when it is running between the guide eye and the surface of the delivery bobbin the thread revolvingly travels in the form of a thread balloon. The guide eye is arranged at a distance from the surface of the delivery bobbin which is determined by experience and by the available space.
During re-piecing the threads after a thread rupture or after a bobbin exchange operation the length of thread required for the re-piecing operation is firstly withdrawn from the delivery bobbin. When the thread withdrawal step is terminated, and thus, the tension of the thread decreases, snarls form in the case of spun yarns which may result in knots which cannot be disentangled. Such knots cause irregularities like, for example, thick locations, which may cause needle breakage in sewing machines. Therefore, the thick locations must be removed during an additional operational step if an unobjectionable or faultless yarn is to be produced.
In case of interruptions in the working operations, i.e. whenever the running-off thread is not continuously led away or withdrawn from the delivery bobbin and if thus no tension acts upon the thread, then parts of the thread coils or turns or whole thread coils or turns may disengage from the surface of the bobbin and form snarls due to the twist originating from the spinning or twisting operation. Upon restarting it may happen, that the snarls do not unravel and are thus introduced into the winding operation. Also, knots can be formed which cause a new interruption at the winding location or may result in an interruption during further processing of the bobbin or the thread, respectively.
Various methods and apparatuses are known which strive to prevent snarl formation. One of the known apparatuses comprises a velour cushion arranged outside the thread balloon region. After withdrawal of the required thread reserve the operator fixedly retains the thread end with one hand and leads the thread coming from the bobbin to the cushion and presses the same against the latter with the other hand. No snarls now form between the bobbin and the cushion provided that the thread extends tangentially from the bobbin. The length of thread which can be obtained in this manner is very modest and will already become disengaged from the cushion when subjected to even the slightest pull or tension.
Also, clamping devices are already known which serve to retain the thread. However, also such clamping devices are unsatisfactory since for inserting the thread the operator first must open the clamping device and thus requires both hands for the operation.
Another apparatus for preventing threads snarls forming in running or travelling yarns as known, for example, from German Patent Publication No. 3,120,430, comprises a brush ring placed intermediate the yarn unwinding or delivery bobbin and a yarn guiding element. The elastic bristles of the brush ring project into the thread balloon and maintain the unwinding yarn taut.
The aforementioned device is totally unsatisfactory for use with fine yarns, and particularly with doubling machines, since the balloon is not freely formed, and thus, the yarn cannot run-off neatly from the surface of the bobbin. Furthermore, an automatic start-up of the machine is not possible without additional thread guiding means which hold the yarn disengaged from the brush ring.